metamorphic

Coarse-grained metamorphic rock, likely amphibolite or hornblende gneiss

Amphibolite; predominantly hornblende amphibole and plagioclase feldspar, possibly with quartz and biotite

AI-generated identification · may be incorrect

Dark gray-green, speckled, granular and weakly foliated, with dull to slightly vitreous luster; amphibole hardness ~5–6 and feldspar ~6, with no obvious cleavage visible at this resolution. Specific gravity is commonly about 2.9–3.2.

Identified September 1, 2026More metamorphic →

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At a glance

Common name: Coarse-grained metamorphic rock, likely amphibolite or hornblende gneiss
Scientific name: Amphibolite; predominantly hornblende amphibole and plagioclase feldspar, possibly with quartz and biotite
Category: metamorphic
Identified: September 1, 2026
Method: Standard

AI Estimated Value

About $2–$15 for an ordinary hand specimen; $20–$75 for an attractive polished or unusually textured specimen.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Formed when basaltic or gabbroic rock underwent medium- to high-grade regional metamorphism, commonly during Precambrian to younger mountain-building events. The exact age cannot be determined from the photograph.

Uses & applications

Used locally as crushed aggregate, road stone, riprap, and dimension stone; attractive polished pieces may be sold as decorative specimens, but it is not generally a gemstone.

Geological facts

Amphibolite’s green-black color reflects abundant hornblende, while lighter grains are commonly plagioclase. Strong alignment of amphibole crystals may produce a gneissic or schistose texture.

Field identification & locations

Look for a dense greenish-black rock with interlocking crystals, amphibole splinters, and possible foliation; a streak, hardness, and thin-section test would improve identification. Common in metamorphic belts worldwide, including the Appalachians, Canadian Shield, and Scandinavia.